Cancer of the pancreas is the fourth and fifth leading cause of cancer deaths among men and women, respectively, in the United States today. Because of the location of the tumor and its silent growth, the overwhelming majority of patients present at a late stage of tumor growth when the disease is not responsive to traditional treatment methodologies. During the past few years of the currently active grant, we demonstrated that mAb-PAM4, reactive with a pancreatic cancer mucin, was able to distinguish pancreatic cancer from normal and inflamed pancreatic tissue; was able to target in a specific manner, and at high concentrations to experimental pancreatic tumors; and was able to cause growth inhibition and/or regression of experimental pancreatic tumors. These data provided rationale for the further development and in vivo clinical application of mAb-PAM4 to be performed as part of the current proposal. In addition to PAM4, mAb-Mu9, reactive with mucin, or a mucin-like molecule will be used for radioimmunodetection and therapy of colorectal cancer. In this Project we intend to examine the nature of the antigens to which these 2 antibodies are directed. We will examine the structure of the immunoreactive epitopes and study their relationship to other peptide and carbohydrate structures within mucin type glycoproteins. In addition, we intend to examine the interaction with antigen and metabolic fate of these antibodies at the molecular and cellular levels. These results will provide information to guide the further development of mAb-based technologies for detection and therapy of antigen positive cancer patients. With the knowledge developed from analyses of antigen structure and antigen:antibody interactions as well as feedback from preclinical and clinical targeting studies we will develop second generation antibodies for use against pancreatic cancer. Finally, we will examine the use of a PAM4-based enzyme immunoassay for the detection and quantitation of antigen in the blood of pancreatic cancer patients in the hope of providing earlier detection with potentially more effective therapeutic outcome. The specificity, sensitivity, and diagnostic accuracy will be determined. In a separate study we will examine the relationship of the blood antigen concentration with tumor burden, as a prelude to its use in monitoring treatment of patients.